Spectrum spotlight

The chemical mapping was performed on the specimens' surfaces before and after AS storage in contact with the composite blocks using a FTIR microspectroscopic system (Spectrum Spotlight FTIR imaging system; Perkin Elmer) with both single-point and imaging mapping mode. Specimens were scanned (4,000 and 650 cm -foot_0 ) at a 4-cm -1 spectral resolution, with 2 scans per pixel. Image size was 80 to 40 µm, using a 6.25-µm pixel resolution. An atmosphere correction was applied to the raw image to subtract the absorbance of water vapor and carbon dioxide. Images were elaborated using the "Spectrum Spotlight" software (Perkin Elmer). The amide I band and the v

Each filter was observed under a Leica DM 500 microscope equipped with camera ICC 50HD (Leica Camera AG, Germany). A visual assessment (shape and color) and counting was conducted to identify all particles retained on the filters according to the physical characteristics of the particles and based on classification described by Free et al. (2014) . The filters were then carried to University of Hull for the validation of the particles. 208 particles were selected from across samples from fish and blanks (approximately 9% of total particles counted), and their identity were confirmed by Fourier-transform infrared microspectroscopy (micro-FT-IR) with a UKAS accredited PerkinElmer Spectrum Spotlight equipped with a mercury-cadmium-telluride focal plane array (FPA) detector (consisting of 16 gold-wired infrared detector elements) cooled with liquid nitrogen (Li et al. 2018) (link).
Analysis was conducted in transmittance mode with particles transferred from filters, using either tweezers or a needle, to be diamond mounted. Spectra were acquired with a minimum of 50 scans at a resolution of 4 cm -1 and matched using a series of polymer library databases (PolyATR, AR Polymer Introductory, NDFIBS, RP, CRIME, FIBRES 3, POLY1, POLYADD1) (PerkinElmer, USA), a hit index of at least 70% match was considered acceptable. 161 of the analyzed particles met this threshold.